Pitch determination systems and methods for aerial roof estimation

ABSTRACT

User interface systems and methods for roof estimation are described. Example embodiments include a roof estimation system that provides a user interface configured to facilitate roof model generation based on one or more aerial images of a building roof. In one embodiment, roof model generation includes image registration, image lean correction, roof section pitch determination, wire frame model construction, and/or roof model review. The described user interface provides user interface controls that may be manipulated by an operator to perform at least some of the functions of roof model generation. In one embodiment, the user interface provides user interface controls that facilitate the determination of pitch of one or more sections of a building roof. This abstract is provided to comply with rules requiring an abstract, and it is submitted with the intention that it will not be used to interpret or limit the scope or meaning of the claims.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/467,244, filed May 15, 2009, which claims benefit of U.S. ProvisionalApplication No. 61/197,904 filed on Oct. 31, 2008, which applicationsare incorporated herein by reference in their entirety.

BACKGROUND

1. Field of the Invention

This invention relates to systems and methods for estimatingconstruction projects, and more particularly, to such systems andmethods for determining roof measurement information based on one ormore aerial images of a roof of a building.

2. Description of the Related Art

The information provided below is not admitted to be part of the presentinvention, but is provided solely to assist the understanding of thereader.

Homeowners typically ask several roofing contractors to provide writtenestimates to repair or replace a roof on a house. Heretofore, thehomeowners would make an appointment with each roofing contractor tovisit the house to determine the style of roof, take measurements, andto inspect the area around the house for access and cleanup. Using thisinformation, the roofing contractor then prepares a written estimate andthen timely delivers it to the homeowner. After receiving severalestimates from different rooting contractors, the homeowner then selectsone.

There are factors that impact a roofing contractor's ability to providea timely written estimate. One factor is the size of the roofcontractor's company and the location of the roofing jobs currentlyunderway. Most roof contractors provide roofing services and estimatesto building owners over a large geographical area. Larger roofcontractor companies hire one or more trained individuals who travelthroughout the entire area providing written estimates. With smallerroofing contractors, the owner or a key trained person is appointed toprovide estimates. With both types of companies, roofing estimates arenormally scheduled for buildings located in the same area on aparticular day. If an estimate is needed suddenly at a distant location,the time for travel and the cost of commuting can be prohibitive. If theroofing contractor is a small company, the removal of the owner or keyperson on a current job site can be time prohibitive.

Another factor that may impact the roofing contractor's ability toprovide a written estimate is weather and traffic.

Recently, solar panels have become popular. In order to install solarpanels, the roof's slope, geometrical shape, and size as well as itsorientation with respect to the sun all must be determined in order toprovide an estimate of the number and type of solar panels required.Unfortunately, not all roofs on a building are proper size, geometricalshape, or orientation for use with solar panels.

SUMMARY

These and other objects are met by the systems and methods disclosedherein that determine and provide roof measurement information about thesizes, dimensions, slopes and orientations of the roof sections of abuilding roof. Roof measurement information may be used to generate aroof estimate report that provides and graphically shows thisinformation. A roof estimation system that practices at least some ofthe techniques described herein may include an image acquisition engine,a roof modeling engine, and a report generation engine. The roofestimation system is configured to generate a model of a roof of abuilding, based on one or more aerial images. In addition, the roofestimation system is configured to determine roof measurementinformation and generate a roof estimate report based on the generatedmodel and/or the determined roof measurement information.

In some embodiments, the roof estimation system includes a userinterface engine which provides access to at least some of the functionsof the roof estimation system. In one embodiment, the user interfaceengine provides interactive user interface components operable by anoperator to perform various functions related to generating a model of aroof of a building, including image registration, lean correction, pitchdetermination, feature identification, and model review and/orcorrection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating example functional elements ofone embodiment of a roof estimation system.

FIGS. 2A-2B illustrate aerial images of a building at a particularaddress.

FIGS. 3A-3F illustrate individual pages of an example roof estimatereport generated by an example embodiment of a roof estimation system.

FIGS. 4A-4F are screen displays illustrating image registration andimage lean correction in an example embodiment. (Also shows leancorrection.)

FIGS. 5A-5D are screen displays illustrating pitch determination in anexample embodiment.

FIGS. 6A-6D are screen displays illustrating model construction andconcurrent display of operator specified roof features in an exampleembodiment.

FIGS. 7A-7C are screen displays illustrating roof model review in anexample embodiment.

FIG. 8 is an example block diagram of a computing system for practicingembodiments of a roof estimation system.

FIG. 9 is an example flow diagram of an image registration routineprovided by an example embodiment.

FIG. 10 is an example flow diagram of a pitch determination routineprovided by an example embodiment.

FIG. 11 is an example flow diagram of concurrent feature display routineprovided by an example embodiment.

DETAILED DESCRIPTION

Embodiments described herein provide enhanced computer- andnetwork-based methods, techniques, and systems for estimatingconstruction projects based on one or more images of a structure.Example embodiments provide a Roof Estimation System (“RES”) that isoperable to provide a roof estimate report for a specified building,based on one or more aerial images of the building. In one embodiment, acustomer of the RES specifies the building by providing an address ofthe building. The RES then obtains one or more aerial images showing atleast portions of the roof of the building. Next, the RES generates amodel of the roof of the building, which is then utilized to determineroof measurement information. The roof measurement information mayinclude measurements such as lengths of the edges of sections of theroof, pitches of sections of the roof, areas of sections of the roof,etc. The model of the roof and/or the roof measurement information isthen used to generate a roof estimate report. The roof estimate reportincludes one or more line drawings of the roof of the building, whichare annotated with information about the roof, such as lengths of theedges of sections of the roof, pitches of sections of the roof, areas ofsections of the roof, etc.

Some embodiments of the roof estimation system include an interactiveuser interface configured to provide access to one or more of thefunctions of the roof estimation system. In one embodiment, the roofestimation system includes user interface controls that facilitate imageregistration, image lean correction, roof model generation, pitchdetermination, and roof model review. Image registration includesaligning, based at least in part on operator inputs, one or more imagesof a building roof to a set of reference points within a singlethree-dimensional (“3D”) grid that is shared between the one or moreimages. Roof model generation includes generating a 3D model of a roof,based at least in part on operator inputs specifying various featuresand/or dimensional attributes of the roof. Roof model generation mayfurther include the determination of the pitches of various planarsections of a roof. Roof model review includes display of a model of aroof, possibly in conjunction with one or more images of the roof, sothat an operator may review the model for accuracy and possibly makeadjustments and/or corrections to the roof model. In other embodiments,all or some of the functions of the roof estimation system may beperformed automatically. For example, image registration may includeautomatically identifying building features for the placement ofreference markers. Further, roof model generation may includeautomatically recognizing features, dimensional attributes, and/orpitches of various planar roof sections of the roof.

The described user interface is also configured to concurrently displayroof features onto multiple images of a roof. For example, in thecontext of roof model generation, an operator may indicate a rooffeature, such as an edge or a corner of a section of the roof, in afirst image of the roof. As the roof estimation system receives theindication of the roof feature, the user interface concurrently displaysthat feature in one or more other images of the roof, so that theoperator may obtain feedback regarding the accuracy of the roof model,the image registration, etc.

In the following, FIGS. 1-3 provide an overview of the operation of anexample roof estimation system. FIGS. 4-7 provide additional detailsrelated an example interactive user interface provided by one embodimentof the roof estimation system. FIGS. 8-11 provide details related toroof estimation system implementation techniques.

1. Roof Estimation System Overview

FIG. 1 is a block diagram illustrating example functional elements ofone embodiment of a roof estimation system. In particular, FIG. 1 showsan example Roof Estimation System (“RES”) 100 comprising an imageacquisition engine 101, a roof modeling engine 102, a report generationengine 103, image data 105, model data 106, and report data 107. The RES100 is communicatively coupled to an image source 110, a customer 115,and optionally an operator 120. The RES 100 and its components may beimplemented as part of a computing system, as will be further describedwith reference to FIG. 8.

More specifically, in the illustrated embodiment of FIG. 1, the RES 100is configured to generate a roof estimate report 132 for a specifiedbuilding, based on aerial images 131 of the building received from theimage source 110. The image source 110 may be any provider of images ofthe building for which a roof estimate is being generated. In oneembodiment, the image source 110 includes a computing system thatprovides access to a repository of aerial images of one or morebuildings. In addition, the aerial images 131 may include imagesobtained via manned or unmanned aircraft (e.g., airplane, helicopter,blimp, drone, etc.), satellite, etc. Furthermore, the aerial images 131may include images obtain via one or more ground-based platforms, suchas a vehicle-mounted camera that obtains street-level images ofbuildings, a nearby building, a hilltop, etc. In some cases, avehicle-mounted camera may be mounted in an elevated position, such as aboom. Example aerial images are described further with reference toFIGS. 2A-2B.

The image acquisition engine 101 obtains one or more aerial images ofthe specified building by, for example, providing an indicator of thelocation of the specified building (e.g., street address, GPScoordinates, lot number, etc.) to the image source 110. In response, theimage source 110 provides to the image acquisition engine 101 the one ormore aerial images of the building. The image acquisition engine 101then stores the received aerial images as image data 105, for furtherprocessing by other components of the RES 100. Obtaining aerial imagesof a specified building may include various forms of geo-coding,performed by the image acquisition engine 101 and/or the image source110. In one embodiment, the image source geo-codes a provided streetaddress into latitude and longitude coordinates, which are then used tolook up (e.g., query a database) aerial images of the provided streetaddress.

Next, the roof modeling engine 102 generates a model of the roof of thespecified building. In the illustrated embodiment, the roof modelingengine 102 generates a three-dimensional (“3D”) model, although in otherembodiments, a two-dimensional (e.g., top-down roof plan) may begenerated instead or in addition. Generating a model of the roof maygenerally include image calibration, in which the distance between twopixels on a given image is converted into a physical length. Imagecalibration may be performed automatically, such as based onmeta-information provided along with the aerial images 131.

A variety of automatic and semi-automatic techniques may be employed togenerate a model of the roof of the building. In one embodiment,generating such a model is based at least in part on a correlationbetween at least two of the aerial images of the building. For example,the roof modeling engine 102 receives an indication of a correspondingfeature that is shown in each of the two aerial images. In oneembodiment, an operator 120, viewing two or more images of the building,inputs an indication in at least some of the images, the indicationsidentifying which points of the images correspond to each other formodel generation purposes.

The corresponding feature may be, for example, a vertex of the roof ofthe building, the corner of one of the roof planes of the roof, a pointof a gable or hip of the roof, etc. The corresponding feature may alsobe a linear feature, such as a ridge or valley line between two roofplanes of the roof. In one embodiment, the indication of a correspondingfeature on the building includes “registration” of a first point in afirst aerial image, and a second point in a second aerial image, thefirst and second points corresponding the substantially the same pointon the roof of the building. Generally, point registration may includethe identification of any feature shown in both aerial images. Thus, thefeature need not be a point on the roof of the building. Instead, it maybe, for example, any point that is visible on both aerial images, suchas on a nearby building (e.g., a garage, neighbor's building, etc.), ona nearby structure (e.g., swimming pool, tennis court, etc.), on anearby natural feature (e.g., a tree, boulder, etc.), etc.

In some embodiments, the roof modeling engine 102 determines thecorresponding feature automatically, such as by employing on one or moreimage processing techniques used to identify vertexes, edges, or otherfeatures of the roof. In other embodiments, the roof modeling engine 102determines the corresponding feature by receiving, from the humanoperator 120 as operator input 133, indications of the feature shown inmultiple images of the building.

In one example embodiment, the RES 100 generates a model of the roof ofthe building in the following manner. First, a set of reference pointsare be identified in each of the images. These reference points areidentified by the operator 120 utilizing a suitable input device, suchas a mouse or joystick. The roof modeling engine 102 then uses thesereference points and any acceptable algorithm to co-register the imagesand reconstruct the three-dimensional geometry of the object identifiedby the reference points. There are a variety of photogrammetricalgorithms that can be utilized to perform this reconstruction. One suchalgorithm used by the RES 100 uses photographs taken from two or moreview points to “triangulate” points of interest on the object inthree-dimensional (“3D”) space. This triangulation can be visualized asa process of projecting a line originating from the location of thephotograph's observation point that passes through a particularreference point in the image. The intersection of these projected linesfrom the set of observation points to a particular reference pointidentifies the location of that point in 3D space. Repeating the processfor all such reference points allows the software to determine a 3Dvolume suitable for building a 3D model of the structure. The choice ofreconstruction algorithm depends on a number of factors such as thespatial relationships between the photographs, the number and locationsof the reference points, and any assumptions that are made about thegeometry and symmetry of the object being reconstructed. Several suchalgorithms are described in detail in textbooks, trade journals, andacademic publications.

In addition, generating a model of the roof of a building may includecorrecting one or more of the aerial images for various imperfections.For example, the vertical axis of a particular aerial image sometimeswill not substantially match the actual vertical axis of its scene. Thiswill happen, for example, if the aerial images were taken at differentdistances from the building, or at a different pitch, roll, or yawangles of the aircraft from which the images were produced. In suchcases, an aerial image may be corrected by providing the operator 120with a user interface control operable to adjust the scale and/orrelative angle of the aerial image to correct for such errors. Thecorrection may be either applied directly to the aerial image, orinstead be stored (e.g., as an offset) for use in model generation orother functions of the RES 100.

Generating a model of the roof of a building further includes theautomatic or semi-automatic identification of features of the roof ofthe building. In one embodiment, one or more user interface controls maybe provided, such that the operator 120 may indicate (e.g., draw, paint,etc.) various features of the roof, such as valleys, ridges, hips,vertexes, planes, edges, etc. As these features are indicated by theoperator 120, a corresponding three-dimensional (“3D”) model may beupdated accordingly to include those features. These features areidentified by the operator based on a visual inspection of the imagesand by providing inputs that identify various features as valleys,ridges, hips, etc. In some cases, a first and a second image view of theroof (e.g., a north and east view) are simultaneously presented to theoperator 120, such that when the operator 120 indicates a feature in thefirst image view, a projection of that feature is automaticallypresented in the second image view. By presenting a view of the 3Dmodel, simultaneously projected into multiple image views, the operator120 is provided with useful visual cues as to the correctness of the 3Dmodel and/or the correspondence between the aerial images.

In addition, generating a model of the roof of a building may includedetermining the pitch of one or more of the sections of the roof. Insome embodiments, one or more user interface controls are provided, suchthat the operator 120 may accurately determine the pitch of each of theone or more roof sections. An accurate determination of the roof pitchmay be employed (by a human or the RES 100) to better determine anaccurate cost estimate, as roof sections having a low pitch aretypically less costly surfaces to repair and/or replace.

The generated model typically includes a plurality of planar roofsections that each correspond to one of the planar sections of the roofof the building. Each of the planar roof sections in the model has anumber of associated dimensions and/or attributes, among them slope,area, and length of each edge of the roof section. Other information mayinclude any information relevant to a roof builder or other entityhaving an interest in construction of, or installation upon, the roof.For example, the other information may include identification ofvalleys, ridges, rakes, eaves, or hip ridges of the roof and/or itssections; roof and/or roof section perimeter dimensions and/or outlines;measurements of step heights between different roof levels (e.g.,terraces); bearing and/or orientation of each roof section; lightexposure and/or shadowing patterns due to chimneys, other structures,trees, latitude, etc.; roofing material; etc? Once a 3D model has beengenerated to the satisfaction of the roof modeling engine 102 and/or theoperator 120, the generated 3D model is stored as model data 106 forfurther processing by the RES 100. In one embodiment, the generated 3Dmodel is then stored in a quality assurance queue, from which it isreviewed and possibly corrected by a quality control operator.

The report generation engine 103 generates a final roof estimate reportbased on a model stored as model data 106, and then stores the generatedreport as report data 107. Such a report typically includes one or moreplan (top-down) views of the model, annotated with numerical values forthe slope, area, and/or lengths of the edges of at least some of theplurality of planar roof sections of the model of the roof. The reportmay also include information about total area of the roof,identification and measurement of ridges and/or valleys of the roof,and/or different elevation views rendered from the 3D model (top, side,front, etc). An example report is illustrated and discussed with respectto FIGS. 3A-3E, below.

In some embodiments, generating a report includes labeling one or moreviews of the model with annotations that are readable to a human user.Some models include a large number of small roof details, such asdormers or other sections, such that applying uniformly sized, oriented,and positioned labels to roof section views results in a visuallycluttered diagram. Accordingly, various techniques may be employed togenerate a readable report, including automatically determining anoptimal or near-optimal label font size, label position, and/or labelorientation, such that the resulting report may be easily read andunderstood by the customer 115.

In addition, in some embodiments, generating a report includesautomatically determining a cost estimate, based on specified costs,such as those of materials, labor, transportation, etc. For example, thecustomer 115 provides indications of material and labor costs to the RES100. In response, the report generation engine 103 generates a roofestimate report that includes a cost estimate, based on the costsprovided by the customer 115 and the attributes of the particular roof,such as area, pitch, etc.

In one embodiment, the generated report is then provided to a customer.The generated report can be represented, for example, as an electronicfile (e.g., a PDF file) or a paper document. In the illustrated example,roof estimate report 132 is transmitted to the customer 115. Thecustomer 115 may be or include any human, organization, or computingsystem that is the recipient of the roof estimate report 132. Forexample, the customer 115 may be a property owner, a property manager, aroof construction/repair company, a general contractor, an insurancecompany, a solar power panel installer, a climate control (e.g.,heating, ventilation, and/or air conditioning) system installer, a roofgutter installer, an awning installer, etc. Reports may be transmittedelectronically, such as via a network (e.g., as an email, Web page,etc.) or by some shipping mechanism, such as the postal service, acourier service, etc.

In some embodiments, one or more of the models stored as model data 106are provided directly to the customer or other computing system, withoutfirst being transformed into a report. For example, a model and/or roofmeasurement information based thereon may be exported and/or transmittedas a data file, in any suitable format, that may be consumed orotherwise utilized by some other computing system, such as acomputer-aided design (“CAD”) tool, a drawing program, a labor andmaterial estimation software, a project management/estimation software,etc.

The RES 100 may be operated by various types of entities. In oneembodiment, the RES 100 is operated by a roof estimation service thatprovides roof estimate reports to customers, such as roofingcontractors, in exchange for payment. In another embodiment, the RES 100is operated by a roof construction/repair company, to generate roofestimate reports that are used internally and/or provided to customers,such as property owners.

In addition, the RES 100 may be operated in various ways. In oneembodiment, the RES 100 executes as a desktop computer application thatis operated by the operator 120. In another embodiment, the RES 100executes as a network-accessible service, such as by a Web server, thatmay be operated remotely by the operator 120 and/or the customer 115.Additional details regarding the implementation of an example roofestimation system are provided with respect to FIG. 8, below.

FIGS. 2A-2B illustrate aerial images of a building at a particularaddress. In the illustrated example, the aerial images are representedas stylized line drawings for clarity of explanation. As noted above,such aerial images may be acquired in various ways. In one embodiment,an aircraft, such as an airplane or helicopter is utilized to takephotographs while flying over one or more properties. Such aircraft maybe manned or unmanned. In another embodiment, a ground-based vehicle,such as a car or truck, is utilized to take photographs (e.g., “streetview” photographs) while driving past one or more properties. In such anembodiment, a camera may be mounted on a boom or other elevating member,such that images of building roofs may be obtained. In anotherembodiment, photographs may be taken from a fixed position, such as atall building, hilltop, tower, etc.

In particular, FIG. 2A shows a top plan (top-down) aerial image 210 of abuilding 200. The roof of the building 200 includes multiple planar roofsections 200 a-200 d. FIG. 2A also shows a second aerial image 211providing a perspective (oblique) view of the building 200. The roofsections 200 a and 200 c are also visible in image 211.

FIG. 2B shows a top-down, wide angle image 212 of the building 200. Theimage 212 includes details of the surrounding areas 220 of the building220. Information about the surrounding areas 220 of the building 220 arein some embodiments used to determine additional cost factors related toa roof estimate. For example, the cleanup of, or access to, a worksiteat building 220 may be complicated by various factors, including asubstantial amount of landscaping; steeply sloped building sites;proximity to environmentally sensitive areas; etc. In such cases, theroof estimation system may automatically increase a cost factor in acorresponding roof estimate report.

In some embodiments, an aerial image has corresponding meta-information.Such meta-information may include details about the type of camera used(e.g., focal length, exposure, etc.), the position of the camera (e.g.,GPS coordinates of the aircraft at the time the image was captured), theorientation of the camera (e.g., the angle of the camera), the timeand/or date the image was captured, etc.

FIGS. 3A-3F illustrate individual pages of an example roof estimatereport generated by an example embodiment of a roof estimation system.As discussed with respect to FIG. 1, a roof estimate report is generatedby the roof estimation system based on one or more aerial images of abuilding. The roof estimate report may be based on a computer model(e.g., a 3D model) of the roof, and includes one or more views of themodel. In this example, the various views of the model are presented asannotated line drawings, which provide information about the roof, suchas the roof section areas, roof section edge lengths, roof sectionpitches, etc. The roof estimate report may be in an electronic format(e.g., a PDF file) and/or paper format (e.g., a printed report). In someembodiments, the roof estimate report may be in a format that may beconsumed by a computer-aided design program.

FIG. 3A shows a cover page 301 of the report and includes the address301 a of a building 301 c and an overhead aerial image 301 b of thebuilding 301 c.

FIG. 3B shows a second page 302 of the report and includes two wideperspective (oblique) views 302 a and 302 b of the building 301 c at theaddress with the surrounding areas more clearly shown.

FIG. 3C shows a third page 303 of the report and includes a line drawing303 a of the building roof showing ridge lines 303 b and 303 c, and acompass indicator 303 d. In addition, a building roof having valleyswould result in a line drawing including one or more valley lines. Theridge and/or valley lines may be called out in particular colors. Forexample, ridge lines 303 b and 303 c may be illustrated in red, whilevalley lines may be illustrated in blue. The line drawing 303 a is alsoannotated with the dimensions of the planar sections of the buildingroof. In this case, the dimensions are the lengths of the edges of theplanar roof sections.

FIG. 3D shows a fourth page 304 of the report and includes a linedrawing 304 a of the building roof showing the pitch of each roofsection along with a compass indicator. The pitch in this example isgiven in inches, and it represents the number of vertical inches thatthe labeled planar roof section drops over 12 inches of horizontal run.The slope can be easily calculated from such a representation usingbasic trigonometry. The use of a numerical value of inches of rise perfoot of run is a well known measure of slope in the roofing industry. Aroof builder typically uses this information to assist in the repairand/or construction of a roof. Of course, other measures and/or units ofslope may be utilized as well, including percent grade, angle indegrees, etc.

FIG. 3E shows a fifth page 305 of the report and includes a line drawing305 a of the building roof showing the square footage of each roofsection along with the total square foot area value. Of course, otherunits of area may be used as well, such as square meters or the numberof “squares” of roofing material required for covering each roofsection.

FIG. 3F shows a fifth page 306 of the report and includes a line drawing306 a of the building roof where notes or comments may be written. Theline drawing 306 a includes a label for each roof section (shown here as“A”, “B”, “C”), such that comments may be conveniently related tospecific roof sections.

In other embodiments, more or less information may be provided, or theillustrated information may be arranged in different ways. For example,the report may be provided in electronic form, such as a PDF file or acomputer aided design software format. In some embodiments, the reportmay be “active” or editable, such that the user of the report may makechanges to the report, based on on-site observations.

2. Roof Estimation System User Interface

FIGS. 4A-4F, 5A-5D, 6A-6D, and 7A-7C describe an example interactiveuser interface provided by one embodiment of the roof estimation system.As noted, the RES 100 described with reference to FIG. 1 includes a userinterface engine 104 that is configured to provide access to one or morefunctions of the RES 100, including image registration (described withrespect to FIGS. 4A-4F), roof pitch determination (described withrespect to FIGS. 5A-5D), roof model construction (described withreference to FIGS. 6A-6D), and roof model review (described with respectto FIGS. 7A-7C).

A. Image Registration

FIGS. 4A-4F are screen displays illustrating image registration andimage lean correction in an example embodiment. In particular, FIG. 4Ashows a user interface screen 400 that is utilized by an operator togenerate a three dimensional model of a roof of a building. The userinterface screen 400 shows a roof modeling project in an initial state,after the operator has specified an address of a building and afterimages of the building have been obtained and loaded into the roofestimation system.

The user interface screen 400 includes a control panel 401 and fiveimages 402-406 of a building roof 407. The control panel 401 includesuser selectable controls (e.g., buttons, check boxes, menus, etc.) forvarious roof modeling tasks, such as setting reference points for theimages, setting the vertical (Z) axis for the images, switching betweendifferent images, saving the model, and the like. Each of the images402-406 provides a different view of the building roof 407. Inparticular, images 402-406 respectively provide substantially top-down,south, north, west, and east views of the building roof 407. Each image402-406 includes four marker controls (also called “reference points” or“registration markers”) that are used by the operator to set referencepoints in the image for purposes of image registration. The registrationmarkers will be described further with respect to an enlargement ofimage portion 408 described with respect to FIGS. 4B-4C, below.

FIGS. 4B-4C show an enlarged view of image portion 408 during theprocess of image registration for image 402, which provides a top-downview of the building roof 407. As shown in FIG. 4B, image portion 408includes the building roof 407 and registration markers 410-413. Themarkers 410-413 are interactive user interface controls that can bedirectly manipulated (e.g., moved, rotated, etc.) by the operator inorder to specify points to use for purposes of image registration. Inparticular, image registration includes determining a transformationbetween each of one or more images and a uniform 3D reference grid. Theuniform 3D reference grid is used as a coordinate system for a 3D modelof the roof. By registering multiple images to the reference grid, anoperator may indicate a roof feature on an image (such as a roof edge),which may then be translated from the coordinate system of the image tothe coordinate system of the reference grid, for purposes of includingof the indicated feature in the 3D model.

Marker 410 is an origin marker control, and includes arms 410 a-410 c.Arms 410 a and 410 b are horizontal arms that are utilized to specifythe X and Y axes (e.g., the horizontal plane) of the reference grid. Arm410 c is a vertical arm that may be utilized to specify the Z axis(e.g., the vertical axis) of the reference grid. The use of the verticalarm to specify the Z axis will be further described with respect to FIG.4E, below.

Typically, markers 410-413 are color coded, such that they may bedistinguished from one another. For example, marker 411-413 may berespectively colored red, blue, and green. Origin marker 410 has adifferent appearance than markers 411-413, so may be of any color. Inother embodiments, markers 411-413 may be distinguished in other ways,such as by utilizing different sized dashed lines, different linethicknesses, etc. In still other embodiments, markers are notdistinguished any way from each other, such as by being of uniformshape, color, etc.

FIG. 4C shows image portion 408 with markers 410-413 after they havebeen placed by an operator. Typically, registration markers are placedat four spatially distributed corners of the roof. As shown in FIG. 4C,the operator has placed markers 410-413 at four different corners of thebuilding roof 407. In particular, the operator first placed the originmarker 410 at the lower left corner of the building roof 407, and hasadjusted (e.g., rotated) the arms 410 a and 410 b to align with themajor horizontal axes of the roof. By adjusting the arms 410 a and 410 bof the origin marker 410, the rotational orientation of markers 411-413is automatically adjusted by the roof estimation system. Next, theoperator places markers 411-413 on some other corners of the roof. Ingeneral, the operator can place registration marker over any rooffeature, but roof corners are typically utilized because they are moreeasily identified by the operator. After the operator is satisfied withthe placement of markers 410-413, the operator typically registers anext image of the building roof 407, as will be described next.

FIGS. 4D-4F illustrate image registration for image 404, which providesa north view of the building roof 407. In particular, FIG. 4D shows theuser interface screen 400 described with reference to FIG. 4A. Here,image 402 has been minimized, while image 404 has been enlarged so thatthe operator may register that image by placing markers on image 404, aswill be described below with respect to an enlarged view of imageportion 418.

FIG. 4E shows an enlarged view of image portion 418 during the processof image registration for image 404. Image portion 418 includes thebuilding roof 407 and registration markers 420-423. Markers 420-423respectively correspond to markers 410-413 described above. Inparticular, marker 420 is an origin marker control that includes arms420 a-420 c. Arms 420 a and 420 b are horizontal arms that are utilizedto specify the X and Y axes of the reference grid. Arm 420 c is avertical arm that may be utilized to specify the Z axis of the referencegrid.

In the example of FIG. 4E, the operator has moved each of markers420-423 to a corner of the roof 407. Note that the markers 420-423 aremoved to roof corners that correspond to those selected by the operatorwith markers 410-413, as described with reference to FIG. 4C. Inparticular, origin marker 420 has been moved to the corner of the roof407 selected with origin marker 410 in image 408; marker 421 has beenmoved to the corner selected with marker 411 in image 408; marker 422has been moved to the corner selected with marker 412 in image 408; andmarker 423 has been moved to the corner selected with marker 413 inimage 408. In addition, markers 420-423 have been rotated, by operatorrotation of the origin marker 420, to align with the major axes of theroof 407.

As noted, the operator can utilize the origin marker 420 to specify thevertical axis of the reference grid. In particular, the operator canadjust (e.g., by dragging with a mouse or other pointing device) arm 420c of marker 420 to specify the vertical (Z) axis of the image. In somecases, aerial images may include some amount of lean, due to theorientation of the aircraft during image capture. For example, pitch,yaw, or roll of an aircraft during the course of image capture mayresult in images that are misaligned with respect to the vertical axisof the building and its roof. Typically, an operator may adjust arm 420c to line up with a feature of a building or roof that is known to besubstantially vertical, such as a wall of a house or a chimney. Then,based on the angle of arm 420 c with respect to the vertical axis of theimage, the roof estimation system can determine a correction between thereference grid and the image.

FIG. 4F shows an enlarged view of image portion 418 after registrationof image 404. Once the operator has placed and adjusted markers 420-423,the operator may direct (e.g., by clicking a button) the roof estimationsystem to register the image to the reference grid, based on thepositions and orientations of markers 420-423. Once the roof estimationsystem registers the image, it provides the operator with feedback sothat the operator may determine the correctness or accuracy of theregistration.

In the example of FIG. 4F, the operator has directed the roof estimationsystem to register image 404, and the roof estimation system has updatedimage portion 418 with registration indicators 430-433. Registrationindicators 430-433 provide the operator with feedback so that theoperator may judge the accuracy of the registration of image 404.

Registration indicator 430 is an origin registration indicator thatincludes two arms 430 a-430 b and three reference grid indicators 430c-430 e, shown as dashed lines. The reference grid indicators 430 c-430e show the vertical axis (430 c) and the two horizontal axes (430 d and430 e) of the reference grid determined based on the placement andorientation of the markers 420-423. Arms 430 a and 430 b correspond tothe placement of arms 420 a-420 c of origin marker 420. If the arms 430a and 430 b do not substantially align with the corresponding referencegrid indicators 430 e and 430 d, then the determined reference grid isout of alignment with the specified axes of the house. Typically, anoperator will return to the view of FIG. 4E to make adjustments toorigin marker, such as adjusting one or more of the vertical orhorizontal axes, in order to refine the registration of the image.Although the arms 430 a-430 b and the reference grid indicators 430c-430 e are here illustrated as solid and dashed lines, in otherembodiments they may be color coded. For example, arms 430 a-430 b maybe red, while reference grid indicators 430 c-430 e may be blue.

Registration indicators 431-433 provide the operator with informationregarding the accuracy of the placement of markers 421-423. Inparticular, each registration indicator 431-433 includes a solidcrosshairs and a reference indicator, shown for example as a dashed line432 a. The crosshair of a registration indicator corresponds to theplacement of a marker. For example, the crosshairs of registrationindicator 431 corresponds to the placement of marker 421 in FIG. 4E. Ifthe reference indicator intersects the center (or substantially near thecenter) of the crosshairs of a registration indicator, then the operatorknows that the placement of the corresponding marker is accurate. On theother hand, if the reference indicator does not intersect the center ofthe crosshairs of a registration indicator, then the operator knows thatthe placement of the corresponding marker is inaccurate. Typically, suchan inaccuracy arises when the placement of markers in the top view ofthe roof does not agree with (correspond to) the placement ofcorresponding markers in another view of the roof. In such cases, theoperator can return to the view of FIG. 4C or 4E to adjust the positionof one or more markers.

After registering image 404, the operator will proceed to registeradditional images of the building roof 407 utilizing a process similarto that described above. In this example, the operator will registerimages 403, 405, and 406. Although the operator is here described asregistering a total of five images, in other cases more or fewer imagesmay be registered.

B. Roof Model Construction

FIGS. 5A-5D and 6A-6C generally illustrate aspects of the process ofroof model generation based on multiple registered images. Inparticular, these figures illustrate the construction of a roof model byan operator. Model generation/construction may include identification ofroof features shown in various images of the roof, such as edges, planarsections, vertexes, and the like, as well as determination of roof pitchand other dimensional attributes of the roof. Each identified rooffeature is incorporated by the roof estimation system into a 3D model ofthe roof, based on a translation between an image in which the featureis identified and the reference grid, as determined by the processdescribed with reference to FIGS. 4A-4F, above.

FIGS. 5A-5D are screen displays illustrating pitch determination in anexample embodiment. In particular, FIG. 5A shows the user interfacescreen 400 after images 402-406 have been registered. In this example,the operator is using a pitch determination control (also called a“pitch determination marker” or “pitch determination tool”) to specifythe pitch of a planar roof section of the building roof 407 visible inimage 406. The pitch determination control will be further described inFIG. 5B, below, with respect to an enlargement of image portion 508.

FIG. 5B shows an enlarged view of image portion 508 during the processof pitch determination for image 406, which provides an east perspectiveview of the building roof 407. As shown in FIG. 5B, the image portion508 includes the building roof 407 and a pitch determination marker 510(also called a “protractor tool”). The pitch determination marker 510 isan interactive user interface control that can be directly manipulatedby the operator in order to specify the pitch of a section of thebuilding roof 407.

The pitch determination marker 510 includes arms 510 a-510 d. Arms 510a-510 c are axes, which are automatically aligned, based on theregistration of image 406, with the major (X, Y, and Z) axes of thebuilding roof. Arm 510 d is a “protractor” arm that is adjustable by theoperator to specify roof pitch.

The marker 510 is typically first moved by the operator to a convenientlocation on the building roof 407, usually corner of a planar section ofthe roof 407. Next, the operator adjusts arm 510 d so that issubstantially aligns with the sloped edge of the planar roof section.Then, the roof estimation system determines the pitch of the roofsection, based on the configuration of the marker 510 with respect tothe image and the reference grid.

After specifying the pitch of a planar roof section, the operator willtypically specify other information about the planar roof section, suchas its outline, as will be described with reference to FIGS. 6A-6D. Notethat as the operator provides additional information about the geometryof the roof 407, the roof estimation system may automatically determinethe pitch and/or other features of at least some of the other planarroof sections, based on the provided geometric information and/orassumptions about roof symmetry or other standard architecturalpractices.

FIG. 5C shows a second type of pitch determination marker being used inthe context of image 403 which provides a south perspective view of thebuilding roof 407. The illustrated pitch determination marker may beused in addition to, or instead of, the pitch determination marker 510described with respect to FIGS. 5A-5B, above. In particular, FIG. 5Cshows a pitch determination marker 520 (also called an “envelope tool”)that includes surfaces 520 a and 520 b. The pitch determination marker520 is an interactive user interface control that can be directlymanipulated by the operator in order to specify the pitch of a sectionof the building roof 407. In particular, the pitch determination marker520 may be moved and/or adjusted so that it appears to lie substantiallyatop two adjacent planar sections of roof 407.

FIG. 5D shows the pitch determination marker 520 after the operator hasused it to specify the pitch of two sections of roof 407. Here, theoperator has moved the marker 520 to a position in which the spine ofthe marker 520 is substantially aligned with the ridge line of roof 407.Then, the operator has adjusted the angle of the surfaces 520 a and 520b so that they appear to lie substantially atop corresponding sectionsof roof 407. Then, the roof estimation system determines the pitch ofthe roof sections, based on the configuration of the marker 520 withrespect to the image and the reference grid. Also illustrated are pitchindicators 521 and 522. Pitch indicator 521 corresponds to the measuredpitch of surface 520 a, and pitch indicator 522 corresponds to themeasured pitch of surface 520 b. As the operator adjusts the angle ofsurfaces 520 a and/or 520 b, the corresponding pitch indicators 521-522are automatically updated to reflect the determined pitch. In thisexample, the pitch of both surfaces is given as 4 inches of rise perfoot of run.

The envelope pitch determination marker 520 may be adjusted in otherways, to specify pitches for types of roofs other than the gabled roofshown in image 403. For example, when measuring pitch of roof sectionsthat form a roof hip, point 520 c may be manipulated by the operator,such as by dragging it to the left or right, to adjust the shape of thesurfaces 520 a and 520 b, so that the surfaces align with the edgesformed by the intersection of the sections that form the roof hip.

FIGS. 6A-6D are screen displays illustrating model construction andconcurrent display of operator specified roof features in an exampleembodiment. In particular, FIGS. 6A-6D illustrate the construction of athree dimensional wire frame model of a building roof, based on thespecification of roof features by an operator. In addition, FIGS. 6A-6Dillustrate the concurrent display of operator specified roof features inmultiple views of a building roof.

FIG. 6A shows the user interface screen 400 after images 402-406 havebeen registered, and after roof pitches have been determined. In thisexample, the operator is specifying sections of roof 407, visible inimage 406, that are to be added to a 3D wire frame model of the roof 407maintained by the roof estimation system. The specification of roofsections will be further described with reference to enlarged portion608 of image 406 in FIG. 6B, below. In addition, as the operatorspecifies roof sections in image 406, the roof estimation systemconcurrently displays the specified roof sections in each of the otherimages 402-405. The concurrent display of operator specified rooffeatures will be further described with reference to enlarged portion609 of image 402 in FIG. 6C, below.

FIG. 6B is an enlarged view of image portion 608 during the process ofwire frame model construction in the context of image 406, whichprovides an east perspective view of the building roof 407. As shown inFIG. 6B, the image portion 608 includes the building roof 407, drawingtool 610, and wire frame 611. The drawing tool 610 (also called a“drawing marker” or a “drawing control”) is an interactive userinterface control that can be directly manipulated by the operator inorder to specify roof features, such as edges, ridges, valleys, corners,etc. In the illustrated embodiment, the operator uses the drawing tool610 to trace or outline planar sections of the roof 407, leading to thegeneration of wire frame 611. The drawing tool 610 may be used toestablish a series of connected line segments that result in a closedpolygon representing a planar roof section. As the operator specifies aplanar roof section in this manner, the roof estimation systemdetermines, based on the image and the reference grid, the geometry ofthe planar roof section, and includes (adds) the specified planar roofsection in a 3D model that corresponds to roof 407.

FIG. 6C is an enlarged view of image portion 609 illustrating theconcurrent display of operator specified roof features, in the contextof image 402, which provides a top plan view of the building roof 407.As the operator specifies roof sections as described with respect toFIG. 6B, the roof estimation system concurrently displays the specifiedroof features in one or more of the other images displayed by the userinterface screen 400. More specifically, image portion 609 includesbuilding roof 407 and wire frame 612. Wire frame 612 corresponds to wireframe 611 constructed by the operator with reference to FIG. 6B, exceptthat wire frame 612 is automatically displayed as a projection from the3D model into the top-down view of image 402. Changes that the operatormakes to wire frame 611 are concurrently displayed by the roofestimation system as wire frame 612 in image portion 609. For example,if a new planar roof section is added by the operator to wire frame 611,the new planar roof section is automatically displayed in wire frame612. By concurrently displaying operator identified features in multipleviews of building roof 407, the operator obtains feedback regarding thecorrectness and/or accuracy of the 3D model or other aspects of themodel generation process, such as image registration and pitchdetermination.

Generally, the roof estimation system can be configured to concurrentlydisplay any operator-identified features, such as corners, ridges,valleys, planar sections, and the like, in multiple views of a building.

Furthermore, the concurrently displayed wire frame 612 is an interactiveuser interface element, in that the operator can make changes to thewire frame 612, which are then concurrently displayed in wire frame 611.Wire frames similar to those described above are also projected by theroof estimation system into images 403, 404, and 405 displayed by theuser interface screen 400. In this manner, the operator can switchbetween various images of the building roof 407, making refinements tothe 3D model by adjusting the wire frame in whichever image is moreconvenient and/or provides a more suitable perspective/view of themodel.

FIG. 6D shows the user interface screen 400 during construction of a 3Dmodel of the building roof 407. In particular, the user interface 400includes a shaded wire frame 613 representation of the 3D modelconstructed as described above. In this view, the operator can reviewthe wire frame 613 in isolation from any images to determine whether thewire frame 613 accurately represents the building roof 407. The wireframe 613 is an interactive user interface component, in that it can bedirectly manipulated (e.g., moved, rotated, resized, etc.). In someembodiments, manipulating the wire frame 613, such as by changing itsshape, results in corresponding changes in the underlying 3D model.

C. Roof Model Review

FIGS. 7A-7C are screen displays illustrating roof model review in anexample embodiment. In particular, FIGS. 7A-7C illustrate varioustechniques to facilitate the review of a roof model by an operator.Reviewing the roof model may include reviewing roof section pitches(e.g., to determine whether they conform to the building roof and/orstandard construction practices), reviewing the shape and/or location ofthe roof model (e.g., to determine whether it substantially conforms tothe building roof), etc.

FIG. 7A shows the user interface screen 400 after the operator hasconstructed a model of the roof 407 using one or more of the images402-406. In this example, a wire frame has been projected onto(superimposed upon) image 402 and annotated with roof section pitches,as will be described further with respect to enlarged portion 708 ofimage 402 in FIG. 7B, below.

FIG. 7B is an enlarged view of image portion 708 during the process ofroof model review in the context of image 402, which provides asubstantially top plan view of the building roof 407. As shown in FIG.7B, the image portion 708 includes a wire frame 710 and labels 711 a-711c that indicate pitches of corresponding sections of roof 407. The wireframe 710 and the illustrated pitches are determined by the roofestimation system based on the pitch determination described withrespect to FIGS. 5A-5D, above, and the operator's specification of thewire frame model described with respect to FIGS. 6A-6D, above.

The wire frame 710 includes multiple vertexes connected by linesegments. Each vertex includes a handle, such as handle 710 a. Thehandles may be directly manipulated (individually or in groups) by theoperator to make adjustments/modifications to the wire frame 710. Forexample, when an operator drags handle 710 a to a new location, the endsof the two line segments connected to handle 710 a will also move to thenew location.

FIG. 7C is an alternative view of the 3D model of roof 407 during theprocess of roof model review. In FIG. 7C, the user interface screen 400includes a wire frame 720 representation of the 3D model of the roof407. The wire frame 720 consists of multiple line segments correspondingto edges of planar roof sections. Each line segment is annotated with alabel, such as label 723, indicating the determined length of thecorresponding roof section edge. Furthermore, some of the line segmentsindicate that they correspond to a particular roof feature. For example,line segments 721 and 722 may be colored (e.g., red) so as to indicatethat they correspond to roof ridges. Other line segments may bedifferently colored (e.g., blue) so as to indicate a correspondence toroof valleys or other features. In addition, the wire frame 720 may bedirectly manipulated by the operator in order to make adjustments to theunderlying model of the roof 407. For example, the operator couldincrease or decrease the length of line segment 721, resulting in achange in the corresponding feature of the 3D model of roof 407.

Note that although the operator is shown, in FIGS. 5-7 above, operatingupon a total of five images, in other cases, fewer images may be used.For example, in some cases fewer images may be available, or some imagesmay provide obstructed views of the building roof, such as due to treecover, neighboring buildings, etc.

3. Implementation Techniques

FIG. 8 is an example block diagram of a computing system for practicingembodiments of a roof estimation system. FIG. 8 shows a computing system800 that may be utilized to implement a Roof Estimation System (“RES”)810. One or more general purpose or special purpose computing systemsmay be used to implement the RES 810. More specifically, the computingsystem 800 may comprise one or more distinct computing systems presentat distributed locations. In addition, each block shown may representone or more such blocks as appropriate to a specific embodiment or maybe combined with other blocks. Moreover, the various blocks of the RES810 may physically reside on one or more machines, which use standardinter-process communication mechanisms (e.g., TCP/IP) to communicatewith each other. Further, the RES 810 may be implemented in software,hardware, firmware, or in some combination to achieve the capabilitiesdescribed herein.

In the embodiment shown, computing system 800 comprises a computermemory (“memory”) 801, a display 802, one or more Central ProcessingUnits (“CPU”) 803, Input/Output devices 804 (e.g., keyboard, mouse,joystick, track pad, CRT or LCD display, and the like), othercomputer-readable media 805, and network connections 806. The RES 810 isshown residing in memory 801. In other embodiments, some portion of thecontents, some of, or all of the components of the RES 810 may be storedon and/or transmitted over the other computer-readable media 805. Thecomponents of the RES 810 preferably execute on one or more CPUs 803 andgenerate roof estimate reports, as described herein. Other code orprograms 830 (e.g., a Web server, a database management system, and thelike) and potentially other data repositories, such as data repository820, also reside in the memory 801, and preferably execute on one ormore CPUs 803. Not all of the components in FIG. 8 are required for eachimplementation. For example, some embodiments embedded in other softwaredo not provide means for user input, for display, for a customercomputing system, or other components.

In a typical embodiment, the RES 810 includes an image acquisitionengine 811, a roof modeling engine 812, a report generation engine 813,an interface engine 814, and a roof estimation system data repository816. Other and/or different modules may be implemented. In addition, theRES 810 interacts via a network 850 with an image source computingsystem 855, an operator computing system 865, and/or a customercomputing system 860.

The image acquisition engine 811 performs at least some of the functionsof the image acquisition engine 101 described with reference to FIG. 1.In particular, the image acquisition engine 811 interacts with the imagesource computing system 855 to obtain one or more images of a building,and stores those images in the RES data repository 816 for processing byother components of the RES 810. In some embodiments, the imageacquisition engine 811 may act as an image cache manager, such that itpreferentially provides images to other components of the RES 810 fromthe RES data repository 816, while obtaining images from the imagesource computing system 855 when they are not already present in the RESdata repository 816. In other embodiments, images may be obtained in an“on demand” manner, such that they are provided, either by the imageacquisition engine 811 or the image source computing system 855,directly to modules of the RES 810 and/or the operator computing system865, without intervening storage in the RES data repository 816.

The roof modeling engine 812 performs at least some of the functions ofthe roof modeling engine 102 described with reference to FIG. 1. Inparticular, the roof modeling engine 812 generates a model based on oneor more images of a building that are obtained from the RES datarepository 816 or directly from the image source computing system 855.As noted, model generation may be performed semi-automatically, based onat least some inputs received from the computing system 865. Inaddition, at least some aspects of the model generation may be performedautomatically, based on image processing and/or image understandingtechniques. After the roof modeling engine 812 generates a model, itstores the generated model in the RES data repository 816 for furtherprocessing by other components of the RES 810.

The report generation engine 813 performs at least some of the functionsof the report generation engine 103 described with reference to FIG. 1.In particular, the report generation engine 813 generates roof reportsbased on models stored in the RES data repository 816. Generating a roofreport may include preparing one or more views of a given 3D model of aroof, annotating those views with indications of various characteristicsof the model, such as dimensions of sections or other features (e.g.,ridges, valleys, etc.) of the roof, slopes of sections of the roof,areas of sections of the roof, etc. In some embodiments, the reportgeneration engine 813 facilitates transmission of roof measurementinformation that may or may not be incorporated into a roof estimatereport. For example, the roof generation engine 813 may transmit roofmeasurement information based on, or derived from, models stored in theRES data repository 816. Such roof measurement information may beprovided to, for example, third-party systems that generate roofestimate reports based on the provided information.

The interface engine 814 provides a view and a controller thatfacilitate user interaction with the RES 810 and its various components.For example, the interface engine 814 implements a user interface engine104 described with reference to FIG. 1. Thus, the interface engine 814provides an interactive graphical user interface that can be used by ahuman user operating the operator computing system 865 to interact with,for example, the roof modeling engine 812, to perform functions relatedto the generation of models, such as point registration, featureindication, pitch estimation, etc. In other embodiments, the interfaceengine 814 provides access directly to a customer operating the customercomputing system 860, such that the customer may place an order for aroof estimate report for an indicated building location. In at leastsome embodiments, access to the functionality of the interface engine814 is provided via a Web server, possibly executing as one of the otherprograms 830.

In some embodiments, the interface engine 814 provides programmaticaccess to one or more functions of the RES 810. For example, theinterface engine 814 provides a programmatic interface (e.g., as a Webservice, static or dynamic library, etc.) to one or more roof estimationfunctions of the RES 810 that may be invoked by one of the otherprograms 830 or some other module. In this manner, the interface engine814 facilitates the development of third-party software, such as userinterfaces, plug-ins, adapters (e.g., for integrating functions of theRES 810 into desktop applications, Web-based applications, embeddedapplications, etc.), and the like. In addition, the interface engine 814may be in at least some embodiments invoked or otherwise accessed viaremote entities, such as the operator computing system 865, the imagesource computing system 855, and/or the customer computing system 860,to access various roof estimation functionality of the RES 810.

The RES data repository 816 stores information related the roofestimation functions performed by the RES 810. Such information mayinclude image data 105, model data 106, and/or report data 107 describedwith reference to FIG. 1. In addition, the RES data repository 816 mayinclude information about customers, operators, or other individuals orentities associated with the RES 810.

In an example embodiment, components/modules of the RES 810 areimplemented using standard programming techniques. For example, the RES810 may be implemented as a “native” executable running on the CPU 803,along with one or more static or dynamic libraries. In otherembodiments, the RES 810 is implemented as instructions processed byvirtual machine that executes as one of the other programs 830. Ingeneral, a range of programming languages known in the art may beemployed for implementing such example embodiments, includingrepresentative implementations of various programming languageparadigms, including but not limited to, object-oriented (e.g., Java,C++, C#, Matlab, Visual Basic.NET, Smalltalk, and the like), functional(e.g., ML, Lisp, Scheme, and the like), procedural (e.g., C, Pascal,Ada, Modula, and the like), scripting (e.g., Perl, Ruby, Python,JavaScript, VBScript, and the like), declarative (e.g., SQL, Prolog, andthe like).

The embodiments described above may also use well-known synchronous orasynchronous client-server computing techniques. However, the variouscomponents may be implemented using more monolithic programmingtechniques as well, for example, as an executable running on a singleCPU computer system, or alternatively decomposed using a variety ofstructuring techniques known in the art, including but not limited to,multiprogramming, multithreading, client-server, or peer-to-peer,running on one or more computer systems each having one or more CPUs.Some embodiments execute concurrently and asynchronously, andcommunicate using message passing techniques. Equivalent synchronousembodiments are also supported by an RES implementation. Also, otherfunctions could be implemented and/or performed by eachcomponent/module, and in different orders, and by differentcomponents/modules, yet still achieve the functions of the RES.

In addition, programming interfaces to the data stored as part of theRES 810, such as in the RES data repository 816, can be available bystandard mechanisms such as through C, C++, C#, and Java APIs; librariesfor accessing files, databases, or other data repositories; throughscripting languages such as XML; or through Web servers, FTP servers, orother types of servers providing access to stored data. For example, theRES data repository 816 may be implemented as one or more databasesystems, file systems, memory buffers, or any other technique forstoring such information, or any combination of the above, includingimplementations using distributed computing techniques.

Also, the example RES 810 can be implemented in a distributedenvironment comprising multiple, even heterogeneous, computer systemsand networks. For example, in one embodiment, the image acquisitionengine 811, the roof modeling engine 812, the report generation engine813, the interface engine 814, and the data repository 816 are alllocated in physically different computer systems. In another embodiment,various modules of the RES 810 are hosted each on a separate servermachine and are remotely located from the tables which are stored in thedata repository 816. Also, one or more of the modules may themselves bedistributed, pooled or otherwise grouped, such as for load balancing,reliability or security reasons. Different configurations and locationsof programs and data are contemplated for use with techniques ofdescribed herein. A variety of distributed computing techniques areappropriate for implementing the components of the illustratedembodiments in a distributed manner including but not limited to TCP/IPsockets, RPC, RMI, HTTP, Web Services (XML-RPC, JAX-RPC, SOAP, and thelike).

Furthermore, in some embodiments, some or all of the components of theRES are implemented or provided in other manners, such as at leastpartially in firmware and/or hardware, including, but not limited to oneor more application-specific integrated circuits (ASICs), standardintegrated circuits, controllers (e.g., by executing appropriateinstructions, and including microcontrollers and/or embeddedcontrollers), field-programmable gate arrays (FPGAs), complexprogrammable logic devices (CPLDs), and the like Some or all of thesystem components and/or data structures may also be stored (e.g., assoftware instructions or structured data) on a computer-readable medium,such as a hard disk, a memory, a network, or a portable media article tobe read by an appropriate drive or via an appropriate connection. Thesystem components and data structures may also be stored as data signals(e.g., by being encoded as part of a carrier wave or included as part ofan analog or digital propagated signal) on a variety ofcomputer-readable transmission mediums, which are then transmitted,including across wireless-based and wired/cable-based mediums, and maytake a variety of forms (e.g., as part of a single or multiplexed analogsignal, or as multiple discrete digital packets or frames). Suchcomputer program products may also take other forms in otherembodiments. Accordingly, embodiments of this disclosure may bepracticed with other computer system configurations.

FIG. 9 is an example flow diagram of an image registration routineprovided by an example embodiment. The illustrated routine 900 may beprovided by, for example, execution of the roof estimation system 810described with respect to FIG. 8. The illustrated routine 900facilitates image registration based upon operator indicatedregistration points and/or image lean corrections.

More specifically, the routine begins in step 901, where it displays, ona user interface screen, an aerial image of a building having a roof. Aspart of the user interface screen, the routine also displays userinterface controls such as markers that may be used by an operator forpurposes of image registration and/or lean correction, as described withreference to FIG. 4A, above.

In step 902, the routine receives, via one or more registration markers,indications of one or more points on the aerial image. The registrationmarkers are manipulated by the operator to specify points on the aerialimage, as described with reference to FIGS. 4A-4E. Typically, the pointsare visually identifiable features, such as corners of the roof of thebuilding. For example, if the roof has four corners (e.g., a northwest,southwest, northeast, and southwest corner) the operator may place oneregistration marker on each of the four corners as shown in the aerialimage. Then, the positions (e.g., coordinates on the aerial image) ofthe markers are transmitted to the routine for use in registering theaerial image, as described below.

In step 903, the routine receives, via a lean correction marker, anindication of the vertical axis of the building roof. In at least somecases, the aerial image of the building is out of alignment with respectto the vertical axis of the building. This may be caused, for example,by pitch, roll, and/or yaw experienced by the aircraft during theprocess of photographing the building. To correct for such misalignment,the lean correction marker is manipulated by the operator to indicate avertical axis of the building. Typically, the operator aligns the leancorrection marker with known, substantially vertical feature of thebuilding, such as a chimney, wall corner, etc., as described withreference to FIG. 4E, above. After the operator has aligned the leancorrection marker, the position (e.g., angle of the marker, coordinatesof the endpoints of the marker, etc.) of the lean correction marker istransmitted to the routine for use in registering the aerial image, asdescribed below.

Particular benefits may be obtained from lean correction performed inthe context of an overhead, or “top down,” view. An “overhead lean”occurs when the camera is not directly overhead with respect to thebuilding when the photo is taken. In some cases, leans in excess of 5degrees have been observed in “top down” photos. Furthermore, unlikeoblique, perspective views, a top-down lean is typically less likely toinclude a convenient visual marker that provides sufficient angle toassess the lean direction and magnitude, such as the edge of thebuilding or a tall chimney. An overhead lean affects the perceivedlocation of the roof lines in a top down view. This effect is amplifiedas the pitch of the roof increases and/or as the vertical separationbetween disconnected roof sections increases. Without lean correction,superimposing a wire frame over the visible ridgelines (and otherfeatures of a building that reside at different elevations) may produceasymmetries in otherwise symmetric structures. Further, an absence oflean correction may introduce errors in pitch estimation, as the wireframe may not appear consistent between top and oblique view points.More specifically, without top view lean correction, the positions forthe roof lines in an otherwise correct (i.e., accurate with respect tothe actual geometry of the roof) wire frame will typically not line upon the visible roof lines in the overhead reference photo. This oftenleads the user (or software) to either introduce errors by incorrectlydrawing the wire frame to the image lines or perform a subjectivedetermination of where and how to shift the wire frame lines off theimage lines to produce a correct model. Top view lean correction allowsthe roof estimation system to trace to, or substantially to, the actualroof lines seen in the top image while still producing an accurate wireframe model.

Image misalignment may be specified in other ways. For example, in otherembodiments, the operator may instead rotate the image to a position inwhich the building appears to be in a substantially vertical position.Then, the angle of rotation of the image may be transmitted to theroutine for use in registering the aerial image.

In step 904, the routine registers, based on the received indications ofthe points and/or the received indication of the vertical axis, theaerial image to a reference grid. Registering the image to a referencegrid may include determining a transformation between the reference gridand the image, based on the indicated points and/or the indicatedvertical axis. Determining such a transformation may be based on otherinformation as well, such as meta-information associated with the aerialimage. In some embodiments, the aerial image has correspondingmeta-information that includes image capture conditions, such as cameratype, focal length, time of day, camera position (e.g., latitude,longitude, and/or elevation), etc.

In step 905, the routine determines whether there are additional aerialimages to be registered, and if so, returns to step 901, else proceedsto step 906. During execution of the loop of steps 901-905, the operatortypically indicates, for each registration marker, the same feature(e.g., corner) of the roof as shown in each of multiple images, suchthat the routine can register the multiple images to a single, uniformreference grid. Upon completion of the registration process, the routinehas determined a uniform coordinate system for the multiple aerialimages, for use during other phases of model construction, such as pitchdetermination or feature identification.

In step 906, the routine generates a three-dimensional model based atleast in part on the aerial image(s) and the reference grid. Asdiscussed above with reference to FIGS. 5A-5D and 6A-6D, modelgeneration includes identification of roof features shown in variousimages of the roof, such as edges, planar sections, vertexes, and thelike, as well as determination of roof pitch and other dimensionalattributes of the roof. In other embodiments, the routine performs otherfunctions with the registered images, such as storing them for later use(e.g., by an automated model generation module), transmitting them toanother computing (e.g., for use in a third-party design application),etc. After step 906, the routine ends.

Note that in at least some embodiments, aspects of the routine 900 maybe performed in an automated manner. For example, operations discussedabove as being performed by an operator, such as the determination ofthe location of image registration points of step 902 and/or theindication of lean of step 903, may be performed by automated imageprocessing techniques.

FIG. 10 is an example flow diagram of a pitch determination routineprovided by an example embodiment. The illustrated routine 1000 may beprovided by, for example, execution of the roof estimation system 810described with respect to FIG. 8. The illustrated routine 1000facilitates the determination of the pitch of a section of a roof, bydisplaying a pitch determination marker and modifying a 3D model of aroof based on an indication of roof pitch received via the pitchdetermination marker.

More specifically, the routine begins at step 1001 where it displays anaerial image of a building having a roof comprising a plurality ofplanar roof sections that each have a corresponding pitch. The aerialimage is displayed in the context of a user interface screen, such as isdescribed with reference to FIGS. 4A-6C, above. The aerial images may bereceived from, for example, the image source computing system 855 and/orfrom the RES data repository 816 described with reference to FIG. 8. Asdiscussed above, aerial images may be originally created by camerasmounted on airplanes, balloons, satellites, etc. In some embodiments,images obtained from ground-based platforms (e.g., vehicle-mountedcameras) may be used instead or in addition.

In step 1002, the routine displays a pitch determination marker operableto indicate pitch of a planar roof section. The pitch determinationmarker may be, for example, a pitch determination marker 510(“protractor tool”) or 520 (“envelope tool”), such as are respectivelydescribed with respect to FIGS. 5B and 5C, above. The routine displaysthe pitch determination marker by, for example, presenting it on a userinterface screen displayed on a computer monitor or other displaydevice. The pitch determination marker is a direct manipulation userinterface control, in that an operator may manipulate it (e.g., adjustan angle, change its shape, alter its position, etc.) in order toindicate pitch of a planar roof section. Additional details regardingpitch determination controls are provided with respect to FIGS. 5A-5D,above.

In step 1003, the routine receives, via the displayed pitchdetermination marker, an indication of the pitch of one of the pluralityof planar roof sections of the roof of the building. Receiving anindication of the pitch includes receiving an indication (e.g., via anevent, callback, etc.) that the marker has been manipulated by theoperator, and then determining an angle based on the shape and/orposition of the marker. In some embodiments, such an indication may bereceived on an event driven basis, such as every time the marker ismanipulated in some manner. In other embodiments, the routine may pollthe marker from time to time to determine its current state. Inaddition, the operator may explicitly indicate that the current state ofthe marker is to be transmitted to the routine, such as by pressing abutton or other indication.

In step 1004, the routine modifies a three-dimensional model of the roofbased on the received indication of the pitch of the one planar roofsection. Modifying the 3D model of the roof includes associating theindicated pitch with a portion of the model corresponding to the oneplanar roof section. For example, the 3D model may include one or moredata structures representing planar roof sections, and the indicatedpitch may be included as part of the data structure representing the oneplanar roof section. In some embodiments, the 3D model may not at thispoint include representations of the planar roof sections, such asbecause the operator has not yet specified them. In such a case, theroutine may store the indicated pitch in association with the locationand orientation at which the pitch was specified by the operator, asdetermined from the aerial image. Then, at a later time, when theoperator specifies a roof section that has the same orientation as thestored pitch and that includes or is near the stored location, the roofestimation system can store the indicated pitch in association with thespecified roof section.

After step 1004, the routine ends. In other embodiments, the routine mayinstead return to step 1001, to determine the pitch for another planarroof section (of the same or different roof).

FIG. 11 is an example flow diagram of concurrent feature display routineprovided by an example embodiment. The illustrated routine 1100 may beprovided by, for example, execution of the roof estimation system 810described with respect to FIG. 8. The illustrated routine 1100concurrently displays operator indicated features in multiple aerialimages of a building roof.

More specifically, the routine begins in step 1101, where it displays afirst and a second aerial image of a building having a roof, each of theaerial images providing a different view of the roof of the building.The aerial images are displayed in the context of a user interfacescreen, such as is described with reference to FIGS. 6A-6C, above.

In step 1102, the routine receives an indication of a feature of thebuilding shown in the first aerial image. The indication is typicallyreceived via a user interface control, such as a drawing tool or marker,upon its manipulation by an operator. For example, the operator maymanipulate a drawing tool in order to specify one or more features ofthe building roof, such as a corner on the roof, an edge of the roof, anoutline of a section of the roof, etc. In one embodiment, the operatorutilizes a drawing tool to indicate roof section corner points and roofsection edges connecting those corner points. Additional detailsregarding feature indication are provided with respect to FIGS. 6A-6C,above.

In step 1103, the routine modifies a three-dimensional model of the roofbased on the received indication of the feature of the building.Modifying the 3D model may include adding or updating the indicatedfeature to a wire frame model of the roof. For example, if the indicatedfeature is a roof section corner point, the corner point will be addedto the 3D model, along with the location (e.g., the X, Y, and Z positionof the point) of the point. The location of the point is automaticallydetermined based on a translation of the position of the point in theimage to a point in the uniform reference grid associated with theimage. If the indicated feature is a roof section edge, the edge will beadded to the 3D model, such as by associating the edge with two pointscorresponding to the end points of the edge. Higher-level features canalso be indicated. For example, a planar roof section may be indicatedby “closing” a sequence of two or more connected line segments, tocreate a closed polygon that represents the outline or perimeter of theplanar roof section.

In step 1104, the routine concurrently displays a projection of thefeature from the modified three-dimensional model onto the first andsecond aerial images. In one embodiment, displaying the feature from themodified three-dimensional model includes projecting thethree-dimensional model onto both the first and second aerial images.For example, if the first image (for which the indicated feature wasreceived) provides a west view of the building, and the second imageprovides an east view of the building, the routine will concurrentlydisplay a projection of the indicated feature from the 3D model ontoboth the first and second images. The projection of the indicatedfeature into the second image is based at least in part on a translationfrom the position of the feature in the reference grid to a position inthe second image. In addition, the concurrent display onto two or moreimages occurs at substantially the same time (within a short timeinterval, at times that are substantially coincident) as the indicationof the feature of the building in step 1102, giving the operator theillusion that as they are indicating a feature in the first image, thefeature is being simultaneously projected into the second image.

After step 1104, the routine ends. In other embodiments, the routine mayinstead return to step 1101, to perform an interactive loop of steps1101-1104 with the operator, so that the routine can concurrentlydisplay multiple features as they are indicated by the operator. Notethat in such an embodiment, each iteration of the loop of steps1101-1104 may be performed at near real-time speeds, so as to provide afluid, interactive model generation experience for the operator enablingthe operator to drag, draw, or otherwise indicate/manipulate features ina first image and view the results of their work concurrently projectedinto a second image.

All of the above U.S. patents, U.S. patent application publications,U.S. patent applications, foreign patents, foreign patent applicationsand non-patent publications referred to in this specification and/orlisted in the Application Data Sheet, including but not limited to U.S.Provisional Patent Application No. 61/197,904, entitled “USER INTERFACESYSTEMS AND METHODS FOR ROOF ESTIMATION,” filed Oct. 31, 2008, areincorporated herein by reference, in their entireties.

From the foregoing it will be appreciated that, although specificembodiments have been described herein for purposes of illustration,various modifications may be made without deviating from the spirit andscope of the present disclosure. For example, the methods, systems, andtechniques for generating and providing roof estimate reports discussedherein are applicable to other architectures other than the illustratedarchitecture or a particular roof estimation system implementation.Also, the methods and systems discussed herein are applicable todiffering network protocols, communication media (optical, wireless,cable, etc.) and devices (such as wireless handsets, electronicorganizers, personal digital assistants, portable email machines, gamemachines, pagers, navigation devices such as GPS receivers, etc.).Further, the methods and systems discussed herein may be utilized byand/or applied to other contexts or purposes, such as by or for solarpanel installers, roof gutter installers, awning companies, HVACcontractors, general contractors, and/or insurance companies.

The invention claimed is:
 1. A computer-implemented process in a roofestimation system comprising: displaying, by the roof estimation system,a graphical user interface including a first aerial image of a roofstructure of a building and also at least one first visual marker thatis moveable by a user in a same display window as the first aerial imagewhile said first aerial image is displayed within the graphical userinterface; moving the first visual marker with respect to the firstaerial image of the roof structure to a first location in response toinput from the user; storing data in a memory of the computer of thefirst location to which the first visual marker was moved; displaying asecond aerial image of the roof structure of the building, the secondaerial image providing a different view of the roof than the firstaerial image; and displaying a location of a second visual marker on theroof structure of the building in the second aerial image of the roofstructure based on an indication received from the stored data in thememory of the first location on the displayed first aerial image towhich the user had moved the first visual marker; and generating andoutputting a roof estimate report using a report generation engine,wherein the roof estimate report includes one or more top plan views ofa model of the roof annotated with numerical values for correspondingslope, area, or lengths of the edges of at least some of the pluralityof planar roof sections of the model of the roof.
 2. The process ofclaim 1 wherein the least one first visual marker includes four visualmarkers.
 3. The process of claim 1 wherein the at least one locationover the roof structure includes at least four spatially distributedcorners of the roof structure.
 4. The process of claim 1 wherein atleast one first visual marker is an interactive user interface controlthat can be directly manipulated by the user in order to specify pointson the roof structure in the aerial imagery to be used by the roofestimation system to perform image registration.
 5. The process of claim4, further comprising receiving, by the roof estimation system, inputregarding multiple points on the roof structure in the aerial imagerybased on indications received of locations to which the at least onefirst marker had been moved.
 6. The process of claim 5, furthercomprising performing, by the roof estimation system, the imageregistration based on the multiple points on the roof structure in theaerial imagery.
 7. The process of claim 6 wherein the image registrationincludes determining a transformation between each of one or more imagesof the aerial imagery and a uniform three dimensional reference gridbased on the specified multiple points.
 8. The process of claim 1,wherein the at least one first visual marker is a crosshair.
 9. Theprocess of claim 1 wherein the location data is an address of thebuilding.
 10. The process of claim 1 further comprising: enabling, bythe roof estimation system, a user to input location data correspondingto a location of a building; and in response to the input, providing, bythe roof estimation system, access to aerial imagery of a roof structureof the building corresponding to the location data, wherein the locationdata is one or more of: a street address, global positioning coordinatesand a lot number of the building.
 11. The process of claim 1 furthercomprising: performing, by the roof estimation system, roof pitchdetermination of the roof structure based on the at least one locationover the roof structure in the displayed aerial imagery to which theuser moved the least one first visual marker.
 12. The process of claim 1further comprising: performing, by the roof estimation system, digitalwire frame model construction of the roof structure based on the atleast one location over the roof structure in the displayed aerialimagery to which the user moved the least one first visual marker. 13.The process of claim 1 further comprising: performing, by the roofestimation system, image lean correction of the aerial imagery based onthe at least one location over the roof structure in the displayedaerial imagery to which the user moved the least one first visualmarker.
 14. The process of claim 1 further comprising: determining, bythe roof estimation system, roof measurement information of one or moreroof sections of the roof structure based on the at least one locationover the roof structure in the displayed aerial imagery to which theuser moved the least one first visual marker.
 15. The process of claim14 wherein the roof measurement information includes dimension, slopeand orientation of the one or more roof sections of the roof structure.16. A roof estimation system comprising: at least on computer processor;and at least one memory coupled to the at least one computer processorhaving computer executable instructions thereon that, when executed,cause the at least one processor to: provide a graphical user interfaceincluding at least one first visual marker that is moveable by a userover aerial imagery of a roof structure of a building, the aerialimagery including a first aerial image of the roof structure and asecond aerial image of the roof structure that provides a different viewthan the first aerial image, the first visual marker being provided,while said first aerial image is displayed within the graphical userinterface, and moveable by the user to a location over the displayedfirst aerial image; receive an indication of a selection of at least onelocation on the roof structure as a result of detection of movement ofthe at least one first visual marker to the location on the roofstructure in the displayed first aerial image; use the indication of theselection of at the least one location on the roof structure to identifythat location of the roof structure of the building in the aerialimagery; and display at the same location on the roof structure a secondvisual on the roof structure of the building in the second aerial imageof the roof structure based on the indication received of the locationon the displayed first aerial image to which the user had moved thefirst visual marker; and generate and output a roof estimate reportusing a report generation engine, wherein the roof estimate reportincludes one or more top plan views of a model of the roof annotatedwith numerical values for corresponding slope, area, or lengths of theedges of at least some of the plurality of planar roof sections of themodel of the roof.
 17. The system of claim 16 wherein the computerexecutable instructions, when executed, further cause the at least oneprocessor to: determine roof measurement information of one or more roofsections of the roof structure based on the indication of the selectionof at the least one location on the roof structure.
 18. The process ofclaim 17 wherein the roof measurement information includes dimension,slope and orientation of the one or more roof sections of the roofstructure.
 19. A non-transitory computer readable medium having computerexecutable instructions thereon that, when executed, cause at least oneprocessor to: enable a user to input location data corresponding to alocation of a building; in response to input of the location data,provide access to aerial imagery of a roof structure of the building,the aerial imagery including a first aerial image of the roof structureand a second aerial image of the roof structure that provides adifferent view than the first aerial image, corresponding to thelocation data; receive an indication of a selection of at least onelocation on the roof structure indicated as a result of detection ofmovement of at least one first visual marker in a graphical userinterface to the location on the roof structure in the first aerialimage while the first aerial image is displayed within the graphicaluser interface; use the indication of the selection of at the least onelocation on the roof structure to identify a location of the roofstructure of the building in the first aerial image; and display thelocation of a second visual marker corresponding to the first visualmarker on the roof structure of the building in the second aerial imageof the roof structure based on the indication received of the locationon the displayed first aerial image to which the user had moved thefirst visual marker; and generate and output a roof estimate reportusing a report generation engine, wherein the roof estimate reportincludes one or more top plan views of a model of the roof annotatedwith numerical values for corresponding slope, area, or lengths of theedges of at least some of the plurality of planar roof sections of themodel of the roof.
 20. The non-transitory computer readable medium ofclaim 19 wherein the computer executable instructions, when executed,further cause at least one processor to: provide the at least one firstvisual marker is as an interactive user interface control of thegraphical user interface that can be directly manipulated by the user inorder to specify multiple corresponding points on the roof structure indifferent images that comprise the aerial imagery.
 21. A method carriedout using a computer system having a memory, the method comprising:displaying on a visual display a photographic aerial image of a roof ofa building, the roof having a pitch; displaying a pitch determinationmarker on the visual display overlying the photographic aerial image;moving at least a portion of the pitch determination marker from a firstposition to a second position in response to input from a user to alignwith a pitch of the roof in the aerial image; calculating, by thecomputer system, the pitch of the roof based on the pitch determinationmarker being placed in the second position; storing that pitch in thecomputer memory; and outputting the calculated pitch value of the roof.22. The method according to claim 21 wherein the pitch determinationmarker is a protractor tool and the step of moving the pitchdetermination marker from a first position to a second positioncomprises: moving one arm of the protractor tool in response to inputfrom the user.
 23. The method according to claim 21 wherein the pitchdetermination marker is an envelope tool and the step of moving thepitch determination marker from a first position to a second positioncomprises: changing angle of the envelope tool to have spinesubstantially align with a ridge line of the roof and having a firstsurface lie substantially atop a first section of the roof and a secondsurface lie substantially atop a second section of the roof in theaerial image of the roof.
 24. The method according to claim 21 whereinthe step of outputting the calculated value of the pitch includes:displaying the calculated value of the pitch on the visual display. 25.The method according to claim 24 wherein the step of displaying thecalculated value of the pitch on the visual display includes: displayingthe pitch value in a text menu that is adjacent to the aerial image. 26.The method according to claim 24 wherein the step of displaying thecalculated value of the pitch on the visual display includes: displayingthe pitch value on the display screen as a numeric value overlaying atleast some portion of the aerial image itself.